1. Field of the Invention
This invention generally relates to the field of providing substrates with deposits, which in a subsequent step are used for receiving components on the substrate. More particularly, this invention relates to an assembly for dispensing droplets of a viscous medium and a machine for providing a substrate with deposits by means of such an assembly, wherein the deposits are formed by the droplets.
2. Description of the Background Art
A prior art dispensing machine is disclosed in copending patent application U.S. 09/719 237. More particularly, this prior art machine is of a non-contact dispensing, or jetting, type. Said patent application is focused on a certain part of the machine, which part is a new device for dispensing droplets. The device comprises an eject chamber (37; 137) for containing a small volume of the viscous medium prior to the ejection thereof, an eject nozzle (36; 136) communicating with the eject chamber, eject means (22, 25; 122, 135) for rapidly ejecting said medium from the eject chamber through said nozzle, and supply means for feeding said medium into the eject chamber. The supply means comprises a rotatably driven feed screw receiving the medium from a syringe containing the medium and forcing the medium towards the eject chamber. The medium contained within the syringe in turn is pressurised in order to force it out of the outlet of the syringe.
This prior art device works well. However, there is a problem involved in exchanging syringes in the device, particularly when the new syringe contains a different type of medium than the one to be exchanged. In the last mentioned case the operator of the machine has to rinse the portions of the device containing the medium. These portions are, inter alia, the eject chamber, the eject nozzle, and the feed screw. In the case of a non-contact dispensing machine, the rinse of the nozzle and the associated ejection parts is particularly important in order to achieve a good operation. When handling several syringes with different types of medium, it could happen that the operator exchanges a syringe for syringe not containing the proper medium. This causes additional rinsing and substrates may have to be rejected. While the rinse operation is performed the machine is stopped.
Another problem arising when exchanging syringes is that before resuming the production several dispensing operations must be performed, in order to refill the nozzle and the associated ejection parts with the new medium. Some extra ejections should be performed in order to guarantee that the medium is free from air bubbles. An attempt to reduce the exchange time is disclosed in JP-10294557. The time reduction is obtained by arranging a separate syringe holder at the machine. At the holder, a syringe which later on is to be substituted for the one presently used, is pressurised in that an amount of the medium is dispensed into a container. Thereby it is secured that the medium at the outlet of the syringe is free from air bubbles. Consequently, when replacing the syringe presently at use with the new one the application of medium onto a circuit board can be resumed immediately. However, this prior art solution is only useful in machines using the syringe for direct dispensing, and does not improve a machine of the jetting type to the same extent. Since such a machine has a separate ejecting mechanism, which receives the medium from the syringe, this ejecting mechanism still has to be refilled with the new medium before the application operation is resumed.
Additionally, using a new syringe requires input of associated data to the machine. This data input is time consuming and involves a risk for inputting erroneous data.
Consequently, the exchange of syringes causes an undesired fall in production. Additionally, the waste medium is generally environmentally hazardous and has to be carefully taken care of.
The object of this invention is to provide a solution to the above-mentioned problems occurring when changing syringes.
The invention, in one aspect thereof, provides for an assembly for dispensing droplets of a viscous medium, said assembly being releasably mountable in a machine using the assembly for providing a substrate with deposits, and comprising a nozzle, an eject mechanism connected with the nozzle, a viscous medium container connected with the eject mechanism, an assembly property means holding information about properties of the assembly, and signal interface means.
By being releasably mountable the assembly is usable as a separate unit easily exchangeable and containing the medium. Consequently, the operator is relieved from the problem of handling the syringes and rinsing parts of the assembly. Additionally, the problem of handling the waste medium is eliminated. The assembly provides for a recycling system where the whole assembly, when empty of medium, is sent back to the supplier who originally delivered it.
Further, the assembly comprises an assembly property means, which holds information regarding the assembly, such as identity, type and other properties of the viscous medium contained in the container, or the date when it was filled. Consequently, it can be made sure that an assembly containing the proper viscous medium is mounted in the machine. Thereby operator mistakes resulting in improper medium being provided on a substrate can be avoided. Additionally, the down time of the machine is decreased. Further, the information held in the property means can be directly transferred to the machine through the signal interface means, thereby eliminating the above mentioned risk for (manual) erroneous input.
For the purposes of this application, it is to be noted that the term xe2x80x9cdepositsxe2x80x9d should be interpreted as single or groups of viscous medium dots deposited on the substrate; the term xe2x80x9cviscous mediumxe2x80x9d should be interpreted as solder paste, flux, adhesive, conductive adhesive or any other kind of medium used for fastening components on the substrate; and that the term xe2x80x9csubstratexe2x80x9d should be interpreted as a printed circuit board (PCB), a substrate for ball grid arrays (BGA), chip scale packages (CSP), quad flat packages (QFP), and flip-chips or the like.
In another aspect thereof the invention provides for a machine for providing a substrate with deposits by dispensing droplets of a viscous medium onto the substrate, comprising a docking device for receiving an assembly of the above described type, said docking device comprising an assembly support and complementary signal interface means.
In a further aspect thereof the invention provides for a docking device for receiving an assembly of the above described type, said docking device comprising an assembly support and complementary signal interface means.
The docking device facilitates the mounting/dismounting of the assembly at the machine by providing specific means, such as the assembly support and the interface means, simplifying the docking of the assembly. The mounting/dismounting is further facilitated by the assembly support comprising pneumatically operable assembly locking means, enabling a fast mounting/dismounting.
In accordance with another embodiment of the invention, there is provided an exchange assembly support for supporting at least one exchange assembly. By means of this support the invention is additionally improved by providing for an automatic exchange of assemblies at the docking device. Further, change over times are reduced due to the possibility of, while the machine is running, providing the exchange assembly support with new full assemblies, assemblies holding different types of viscous medium, assemblies having different types of nozzles, etc., to be used later on by the machine.
Preferably, said exchange assembly support also comprises complementary signal interface means. Through these signal interface means it is possible to communicate the properties of the assemblies supported in the exchange assembly support to the machine. Thereby, further, operator mistakes can be avoided since each exchange assembly may be placed in an arbitrary position in the exchange assembly support and the machine will still recognise the proper exchange assembly. It is also possible to alert the operator when there is no adequate assembly for current or pending jobs in the assembly support. This gives the advantage of the operator being able to supply new assemblies in time and further machine stoppages are avoided.
In yet another aspect thereof, the invention provides for a method of exchanging an assembly for dispensing droplets of a viscous medium, said assembly being releasably mounted in a machine using the assembly for providing a substrate with deposits, wherein the assembly comprises an assembly holder having first holding means mating with an assembly support of a docking device of the machine, and an assembly property means holding information about properties of the assembly, comprising the steps of:
selecting an exchange assembly;
exchanging the assembly for the exchange assembly; and
transferring property information from the exchange assembly to the machine.
This method, which is possible to perform by means of inventive constructions according to the invention, that is the separate dispensing assembly releasably mountable in a dispensing machine arranged for receiving such an assembly, is advantageous in that the operator of the machine can be relieved of the stressful exchanges of syringes while the machine has to be down. The transfer of property information assures that the correct assembly is mounted.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.